Loud speaker



J. WEINBERGR ET AL.

LOUD SPEAKER Original Filed March 3l, 1927 INVENToRs JUUUS WHNBERGER mvma o F ATT'ORNEY March l, 1932.

Patented vMar. 1, 1,932

' .l UNITED STATES?PATENT? OFFICE JULIUS WEINBERGER AND IRVING-MWOLFF, F NEWYORK, N.- Y., ASSIGNORS T0 RVASDI CORPORATION V0F AMERICA, `.A CORPORATION OIE DELAWARE b v LOUD SPEAKER.

oiiginai'appucauon mea mmh s1, 1927, serial m5179343. Divided and this application' nea anni 24',` Y vmao. serial 110.1146335.

This application is a division of our application filed lMarch 31st, 1927, Serial No.

179,743, now VPatent No. 1,760,862.

e `This invention relatesto the art of sound 5, reproducing devices and deals more specifically with the provision of a loudspeaker device built-in or enclosed by the cabinet of a radio `receiving set or phonograph.

In the usual structure'of the cabinetsjemployed in connection with radio receiving apparatus the rear wall of theJ cabinet isleft open to provide for ventilation of certain of therradio apparatus; It, therefore, follows that when a loudspeaker device is mounted in suchv a cabinet the cabinet acts as a resonator, thus destroying the fidelity of response ofthe loudspeaker, by over-emphasizing certain Vof the frequencies corresponding to the natural Aperiod of the system at resonance. This ef-` fect has been explained in the following way: The space contained within the cabinet rearwardly of the loudspeaker'is a pressure area, while the mouth of the opening at the rear of the cabinet is a high velocity area. This phenomenon may-be better understood from the mechanical analogy in which the air within vthe cabinet rearwardly of the loudspeaker may be considered a spring, while t Y e air at therear opening of the cabinet may be considered a mass which loads the sprin and causes the vibration. The vibrations, o course are originally set up by the movement of the loudspeaker device and when the frequencies emitted from the loudspeaker approximate the frequency corresponding to the natural period of the air cavities the system resonates freely.

' There are two possible ways of overcoming thi's'undesirable effect. The first one is to stop the motion of the air behind the loudspeaker by ymeansof an yenclosure or casing.

The second method is to release the pressure of air within the cabinet, or in other words to cut olf the spring referred to in they above mechanical analogy by providing openings in the front of the cabinet .adj acent to the loud'- speaker. Either one of theseV methods or both in combination have been found to give highly improved results.

' VIt is, therefore, an object of this invention to .provide a built-in loudspeaker device which will give natural'and` reliable character1st1cs of sound reproduction.

It is a further object'of this invention to-kv preyentthe phemonenon or "resonance in a cabinet of a built-in loudspeaker.

Itl is a further object of this invention to provide a loudspeaker construction adapted to give maximum acousticeiiciency of the sound reproducing diaphragm. f

Furtherit is an obJect f this inventionl to provide a built-inloudspeakerin which the range of audible frequencies reproduced a maximum.y

These and other objects of the invention will be apparent -to one skilled in the art from the following description taken in connection with the accompanying drawings in which: Figure 1 is a front elevational view of 'a loudspeaker embodying this invention. A Figure 2 is a side elevational view of the device shown in Figure 1.1`

Figure 3 is a detailedpview of a modifiedV form of casing. Figure 4 is a ing the loudspeaker the cabinet. y

Referring in, detail to the drawings the loudspeaker is seen to comprise a vibratile fragmentary elevation show-l device mounted within` diaphragmll towhich is coupled a rod 12 which-serves to connect the'diaphragm to a driving unit 13 of any well known type. For the purposes of the present disclosurey a cone diaphragmfhas been illustrated as the vibratile" member 'but' it is Lto be understood that the invention doesjnot relate specifically to this type ofdiaphragm, but rather may beA applied to any `and all typeslo'fvibratile diaphra ls nowfknownsuchwas .a'flat disk, a circu ar 'vibrating `membe'r,as well as oval and other shaped cones, in fact, to any loud-k speaker which radiatesto the reark aswell as the'front. fAlsothe particular form of driving 'unit forms no part of the present invention and needs no further description here. Any of the well known types of reproducing units may be employed. 7

Attached to the drivingv unit 13 are the stays o r "sup orts 14 which forma frame in' the shape o atrunoated'rec'tangular pyramid. Of course, other shapes may be conveniently formed but the present has been chosen as a simple and convenient means of support for the cone and driving unit. Joined to the supports 14 is the plate 15 provided with .an aperture 1G, shaped to conform to the base of the vibratile member 11. The edge of the cone 11 is joined circumferentially to the `plate 15 in any suitable manner designed to prov-ide a .so-called free or floating edge. This may be accomplished, for example, by means of a strip 17 of flexible material such as .a sheep-skin or .any 4suitable textile, the strip being in the form of an annular ring shaped to overlap the edge of the cone and the edge for-ming the aperture 16.. The inner circumference of 4the annular strip 17 is attached to the edge of the cone; while the outer circumference is joined to the plate 15. Obviously fother methods of mounting the vibrating element may be employed without departing from the spirit of this invention.

In order -to .overcome tl-ie undesirable effacts described above resulting from the fact that the cabinet `acts :as a resonator', a casing 181aped somewhat similarly -to the support 14 `is provided and arranged with its upper base in a plane between the rear of the vibratile element 11 and the adjacent -side of the reproducing unit. The side portions and the front edge of the casing 18 are spaced from the support 14 and also from the front face ofthe cone asshown ,in Figure 2. The casing `may be made of any convenient material such :as fibre boa-rd, molded compositions, wood or metal 0r felt. A layer of sound absorbent or cushioning material such as felt or .other fibrous materials may be placed upon the inside of the reflector. The specific design of uthe refiector 18 may be Varied widely to obtain themost satisfactory results, depending upon the particular loudspeaker device used therewith.

Openings 21 are provided in the front mounting plate 15 for the ypu-rpose of releasing Vthe spring action of the vibrating air bctween the diaphragm 11 and the casing 18.

Referring in particular now to Figure a, the loudspeaker device and casing are shown mounted in a cabinet 25 of any suitable radio set which may vbe and ordinarily is open at the rear. lThe assembled loudspeaker and casing are mounted within the vcabinet and secured thereto in any convenient manner such as, for example, .by the .support 26 which may be screwed orotherwise attached to the .casing and to the base of the cabinet. The abutment V27 which is joined to the cabinet `cooperates with the adjacent portion of the reflector to hold the same firmly in place. The usual covering or grille 28 may be provided in front of the loudspeaker device.

lhile the modification shown in Figure 4c includes .the reflector member 14 it is to be understood that under .certain conditions it may be found desi `able to eliminate the use of the casing 14 and rely upon the openings 21 in the front mountinfy to eliminate the undesirable resonance efi'ect. Also, while the casing has been disclosed specifically mountedbctween thc vibrating diaphagm and the driving unit, it is to be understood that this casing may be mounted rearwardly of the said unit in accordance with the principlcs of this invention.

Referring to Figure 3 there is shown a `modified form of reflector which is similar to that shown in the preceding figures but which is provided with a packing of felt or other sound absorbent material, which packinc' is of a thickness to practically fill the entire space between the rear of the vibrating diaphragm and the adjacent faces of the reflector' member. The packing material 19 shown in this figure may be held in place in any suitable manner, such as for example, by threads or wires passing therethrough and joined to the casing. The space 24 between the packing 19 and the cone 11 has a thickness of the order of magnitude of one to two inches.

Claims:

1. A loudspeaker comprising a conical daphragm, a member provided with an opening conforming to the periphery of said diaphragm, means providing a flexible connection between the periphery of said diaphragm and said member, a casing engaging said member and extending rearwardly therefrom, said casing having the shape of a fru-stum, and aV driving unit for said diaphragm located out-side of said frustum.

2. An acoustic device comprising a vibrI tile diaj'ihragm, a supporting member for said diaphragm, flexible means connecting the periphery of said diaphragm with said supporting member, a casing having the shape of a frustum positioned to engage said supporting member substantially at its larger base and extending rearwardly therefrom to enclose the rear of said diaphragm, and sound absorbing material disposed within said casing to occupy substantially all of the space between the back of said diaphragm and said casing.

An acoustic device comprising a vibratile diaphragm, a supporting member for said diaphragm. flexible means connecting the periphery of said diaphragm with said supporting mei'nber, a casing having the shape of ay frustum positioned to engage said supporting member substantially at its larger base and extending rearwardly therefrom to enclose the rear of said diaphragm, a mass of' sound absorbing material disposed within said casing to occupy substantially all of the space between the back of said diaphragm and said casing, a driving unit for said diaphragm positioned outside of said Casin", and members connecting said driving unit and said supporting member, said members extending through said casing and sa-id mass of sound absorbing material.

4. A loudspeaker comprising a conical diaphragm, a member provided with an opening commensurate with the peripheral di- Y mensions of said diaphragm, means providing a flexible connection between said diaphragm and said member, a casing substantially engaging said member and extending rearwardly therefrom, said casing having'the Y shape of a frustum, and driving means for .said diaphragm, said frustum shaped casing tially engaging said member and extending rearwardly therefrom, said frustum` shaped casing having a smaller base provided with an opening therethrough, and a driving member connected to said diaphragm and extending through the opening in said base.

6. A loudspeaker comprising a vibratile diaphragm, a supporting member, means providing a flexible connection between the periphery of said diaphragm and said supporting member, a casing substantially engaging said supporting member and extending rearwardly therefrom, said casing'having y the shape of a frustum, a driving unit operatively connected with said diaphragm and positioned outside of said casing, said frustum shaped casing being arranged so that its smallerbase is interposed between said diaphragm `and said driving unit, and Vsound absorbing material disposed within ysaid casing r 7. loudspeaker comprising a conical diaphragm, a member provided with an opening conforming to the periphery of said diaphragm, means providing a flexible connection between the periphery of said diaphragm and said member, a casing substantially engaging said member and extending rearwardly therefrom, said casing having the shape of a frustum, means for maintainin said diaphragm in fixed relation to saicgl member, and a driving member connected yto said diaphragm, said frustum shaped casing being provided with a smaller base having. anopening therein through which said driving member is adapted to extend.

shape of a frustum, a driving unit for said diaphragm, said driving unit being located outside of said frustum, and means for rigidly connecting said driving unit with said supporting member.

9. A loudspeaker comprising a conical diaphragm, a supporting member, means providing a flexible connection between the periphery of said diaphragm and said supporting member, a casing substantially engaging said supporting member and extending rearwardly therefrom, a driving unit for said diaphragm, said casing having the shape of a. frustum the smaller base of which is interposed between said diaphragm and said driving unit, and means separate from said casing for rigidly connectin said driving unit with said supporting mem er.

10. The combination of a casing for a loudspeaker having a conical diaphragm and a driving member attached thereto, with means for preventing free circulation of sound waves from the rear of the diaphragm to the front of said diaphragm, said casing comprising a frustum shaped member open at its larger base and substantially closed at vits smaller base, said smaller base being provided with openings throughr one of which said driving member is adapted to extend, said frustum Vshaped member being imperforate except for saidopenings in its smaller base.

. v J ULIUS WEINBERGER.

IRVING WOLFF.v Y

8. A loudspeaker comprising a conical diaphragm, a supporting member, means providing a flexible connection betweenithe periphery of said diaphragm and said supporting member, a casing substantially engaging said supporting member and extending rearwardly therefrom, said casing having theA 

